Remove FromDIP in wxGetEditHeightFromCharHeight

This caused wxTextCtrl to become to high at higher DPI.

It was added to fix appearance of wxSearchCtrl at high DPI. Remove an unneeded
FromDIP there too, so it gets the same height as a normal wxTextCtrl.
And centre the textctrl inside the searchctrl.

include/wx/msw/private.h

@@ -91,12 +91,13 @@ WXDLLIMPEXP_BASE void wxSetInstance(HINSTANCE hInst);
 // Return the height of a native text control corresponding to the given
 // character height (as returned by GetCharHeight() or wxGetCharSize()).
 //
-// The wxWindow parameter must be valid and used for getting the DPI.
-inline int wxGetEditHeightFromCharHeight(int cy, const wxWindow* w)
+// The wxWindow parameter is currently not used but should still be valid.
+inline int wxGetEditHeightFromCharHeight(int cy, const wxWindow* WXUNUSED(w))
 {
     // The value 8 here is empiric, i.e. it's not necessarily correct, but
     // seems to work relatively well.
-    return cy + w->FromDIP(8);
+    // Don't use FromDIP(8), this seems not needed.
+    return cy + 8;
 }
 
 // Compatibility macro used in the existing code. It assumes that it's called